Behavioral modeling of the IGBT using the Hammerstein configuration

The Hammerstein model configuration, which includes a nonlinear static block followed by a linear dynamic block, is applied to model the static and dynamic characteristics of the insulated gate bipolar transistor (IGBT). Using least-squares methods, the parameters in the behavioral model can be extracted from the electrical measurements of physical devices or from the circuit simulations of physics-based models. A single set of extracted parameters has been found to yield satisfactory efficiency and accuracy for the tested hard- and soft-switched converters under prescribed ranges of operating conditions     

Image compression in digital mammography: effects on computerized detection of subtle microcalcifications

Our previous receiver operating characteristic (ROC) study indicated that the detection accuracy of microcalcifications by radiologists is significantly reduced if mammograms are digitized at 0.1 mm x 0.1 mm. Our recent study also showed that detection accuracy by computer decreases as the pixel size increases from 0.035 mm x 0.035 mm. It is evident that very large matrix sizes have to be used for digitizing mammograms in order to preserve the information in the image. Efficient compression techniques will be needed to facilitate communication and archiving of digital mammograms. In this study, we evaluated two compression techniques: full frame discrete cosine transform (DCT) with entropy coding and Laplacian pyramid hierarchical coding (LPHC). The dependence of their efficiency on the compression parameters was investigated. The techniques were compared in terms of the trade-off between the bit rate and the detection accuracy of subtle microcalcifications by an automated detection algorithm. The mean-square errors in the reconstructed images were determined and the visual quality of the error images was examined. It was found that with the LPHC method, the highest compression ratio achieved without a significant degradation in the detectability was 3.6:1. The full frame DCT method with entropy coding provided a higher compression efficiency of 9.6:1 at comparable detection accuracy. The mean-square errors did not correlate with the detection accuracy of the microcalcifications. This study demonstrated the importance of determining the quality of the decompressed images by the specific requirements of the task for which the decompressed images are to be used. Further investigation is needed for selection of optimal compression technique for digital mammograms.     

Stimulus classes in matching to sample and sequence production: the emergence of numeric relations

We investigated interrelationships among stimulus classes established in matching-to-sample and sequence-production tasks. The analysis focused on the matching and sequencing of quantities, numerals, and arbitrary forms in two individuals with mental retardation. The basic protocol involved: (a) establishing both matching and sequencing performances with some stimuli, (b) training sequencing with a new set of stimuli and assessing whether new matching performances emerged, and (c) training matching with a new set of stimuli and assessing whether new sequencing emerged. The results showed that sequence training did not readily lead to new matching performances, unlike prior research with college students. In contrast, training in matching to sample yielded emergent sequence production; these data support prior studies involving children and adults without developmental disabilities. The results extend prior stimulus class research and suggest an important role for stimulus control processes in the production of generative numeric performances.     

Negation as failure for disjunctive logic programming

We generalize the Negation-as-Failure procedure for disjunctive logic programming. Then we compare our method with related methods in the literature. We also propose a new completion theory for disjunctive logic programs which allows some program clauses to have inclusive meaning and the others exclusive meaning.     

Anticonvulsant and antibiotic prophylaxis in head injury

The evidence for and against the prophylactic use of anticonvulsants and antibiotics in head injury is reviewed. There is a lack of blinded placebo-controlled trials in this area. On balance there is no compelling evidence to support the use of either anticonvulsant or antibiotic prophylaxis in head injury, with the possible exception of antibiotic prophylaxis in compound depressed skull fractures and penetrating brain injuries.     

A PWM method for reduction of switching loss in a full-bridgeinverter

This paper presents the “hybrid pulsewidth modulation” (HPWM) method which requires only two of the four switches in a full-bridge inverter to be pulsewidth-modulated at high frequency, thus significantly reducing the switching losses in the other two switches. For triangular carriers, HPWM has the same frequency spectrum and switching losses as the conventional unipolar PWM (UPWM). A low-frequency model for a fast-switching HPWM full-bridge inverter with high-quality output is described, and is substantiated by experimental data     

Design issues for the transformer in a low-voltage power supplywith high efficiency and high power density

Circuit model, design feasibility, and design tradeoffs are investigated for the transformer in 1.5-5 V power supplies with high efficiency and high power density. The transformer is constructed from a single or a matrix of pot cores and from interleaved planar windings. It has been determined theoretically and verified experimentally that such a transformer is realizable as long as the loss constraint is not severe (e.g. less than 0.5 W transformer loss per 100 W output). The primary source of loss is the winding, not the core, in 1.5 V/turn design. Measures to reduce the transformer height tend to increase transformer loss or volume     

Current red blood cell transfusion practices

The appropriate use of blood transfusions remains variable among health-care institutions and patient populations. Transfusion practices are discussed in this article in relation to medical practice guidelines and utilization review. Specific transfusion practices in the settings of intensive care, orthopedic surgery, and open heart surgery are reviewed. A new, promising approach to improving transfusion outcomes is the use of transfusion algorithms. Transfusion algorithms may prove especially useful if they incorporate point-of-care testing that is both physiologic and patient-specific for transfusion decisions. Transfusion algorithms are discussed and data presented for cardiac surgical adults.     

Inhibition of IL-1 induced tissue factor (TF) synthesis and procoagulant activity (PCA) in purified human monocytes by IL-4, IL-10 and IL-13

Exposure of monocytes to pro-inflammatory cytokines or lipopolysaccharide (LPS) may induce synthesis and expression of tissue factor (TF). In this paper we have focused on the induction of TF-activity in human monocytes by the pro-inflammatory cytokines recombinant human interleukin 1 (rhIL-1 alpha) (rhIL-1 beta) (rhIL-6) and human tumour necrosis factor alpha (rhTNF-alpha), measured as procoagulant activity (PCA) in a microtitre plate-based clot assay. In addition we have studied the modulation of IL-1 alpha/beta induced TF-mRNA and PCA by rhIL-4, rhIL-10 and rhIL13. IL-1 alpha and IL-1 beta induced a concentration dependent increase in TF-activity. Neither IL-6 nor TNF-alpha gave rise to procoagulant activity at the concentrations tested (0.2-20 ng/ml). IL-4, IL-10 and IL-13, all effectively diminished IL-1 alpha/beta induced PCA, shown at the protein- and at the mRNA-level, while cell viability was unaffected. These results add to the previously demonstrated role of IL-4 and IL-10 as inhibitors of LPS-induced TF-activity, showing that these anti-inflammatory cytokines are not specific for LPS-activation but interfere with other stimulating substances such as IL-1, which may be involved in diseases where LPS is not present.